Changed syntax.
Added func_create_backup() to create a backup.
Changed the interface and added class.

Device/Mountpoint:
The user will now not longer be determined for every method by a
parameter, but once by the constructor when the object is created.

FullLocation:
A new class representing a path on a host, possibly on a certain device
with a mountpoint, associated with a specific user. This class effectively
merges path, mountpoint and device into a single class.
Using new FullLocation and made members public.

Changed all the "user,host,path,device..." hunks to instances of the new
FullLocation class to simplify things. In addition to that, removed the
preceding underscores to make all members of Device and Mountpoint public.
Add get_latest_backup() to BackupRepository.

This function does what it says.
Added option for multiple keys.

With this options, instead of raising an exception when two identical keys in
and element are encountered, their values are all merged into a list.
Continued implementing autobackup.py.